Cross Flow Heat Exchanger

ABSTRACT

A heat exchanger for a work vehicle is provided that comprises a tube layer ( 102 ) made of a plurality of elongate tubes ( 108 ) that are spaced apart by gaps ( 112 ) oriented parallel to each other in a first direction; a first fin layer ( 100 ) in the form of a corrugated sheet having a plurality of corrugations, wherein the plurality of corrugations of the first fin layer ( 100 ) facing the tube layer ( 102 ) define channels ( 106 ) for passing therethrough a fluid different from the first fluid; and a first fluid guide layer ( 200 ) formed of a planar sheet that extends across and encloses the plurality of corrugations of the first fin layer ( 100 ) over substantially an entire length of the plurality of corrugations.

FIELD OF THE INVENTION

The invention pertains to heat exchangers. More particularly it relatesto fluid to fluid (e.g. liquid to air) coolers for engine coolant,lubricating oil, or hydraulic fluid used in internal combustion engines,transmissions, and hydraulic circuits of work vehicles.

BACKGROUND

Air cooled heat exchangers, particularly air cooled heat exchangers usedin agricultural harvesters or other work vehicles, are subject to beingplugged. During crop harvesting, agricultural harvesters generatecontaminated air by the activity of crop cleaning fans, engine coolingfans, and the like. The contaminated air contains particulate matter(primarily plant matter) in sizes ranging from several inches in lengthto fine dust particles. This contaminated air surrounds the agriculturalharvester almost as a cloud. It is difficult if not impossible to cleanthis air before it is used and reused in the various heat exchangersemployed on the agricultural harvester. Similar problems exist for otherwork vehicles, such as road graders, bulldozers, tractors, backhoes, andexcavators.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, a heat exchanger fora work vehicle is provided, comprising: a tube layer comprised of aplurality of elongate tubes, wherein the plurality of elongate tubes arespaced apart by gaps and are oriented parallel to each other in a firstdirection, wherein each of the plurality of elongate tubes defines achannel for passing a first fluid therethrough; a first fin layer in theform of a corrugated sheet having a plurality of corrugations, in whichthe plurality of corrugations of the first fin layer extend in a seconddirection transverse to the first direction, and wherein the first finlayer is disposed parallel to the tube layer and on a first side of thetube layer, and wherein each of the plurality of corrugations of thefirst fin layer facing the tube layer define an enclosed channel forpassing therethrough a fluid different from the first fluid; and a firstfluid guide layer formed of a continuous, generally planar sheet thatextends across and encloses the plurality of corrugations of the firstfin layer over substantially an entire length of the plurality ofcorrugations.

The heat exchanger may further comprise a second fin layer in the formof a corrugated sheet having a plurality of corrugations, in which theplurality of corrugations of the second fin layer extend in the seconddirection, and wherein the second fin layer is disposed parallel to thetube layer and on a second side of the tube layer that is opposite tothe first side of the tube layer, and wherein the plurality ofcorrugations of the second fin layer facing the tube layer definechannels for passing therethrough a fluid different from the firstfluid; and a second fluid guide layer formed of a continuous, generallyplanar sheet that extends across and encloses the plurality ofcorrugations of the second fin layer over substantially an entire lengthof the plurality of corrugations.

The first fluid guide layer may extend across and enclose the gaps oversubstantially the entire length of the gaps.

The first fin layer may comprise metal and the first fluid guide layermay comprise metal, and the first fin layer may be bonded to a firstside of the first fluid guide layer by a process selected from a groupcomprising soldering, brazing, and welding.

The tube layer may comprise metal and the tube layer may be bonded to asecond side of the first fluid guide layer by a process selected from agroup comprising soldering, brazing, and welding.

In one arrangement, none of the channels has an interior region that isin fluid communication with an interior region of any of the pluralityof elongate tubes.

The channels may be rectangular or square in cross-section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of a prior art heat exchanger.

FIG. 1B is a front view of the prior art heat exchanger of FIG. 1A.

FIG. 2 is an exploded perspective view of a heat exchanger in accordancewith the present invention.

FIG. 3A is a fragmentary cross-sectional view of the assembled heatexchanger arrangement of FIG. 2 taken at section line 3A-3A.

FIG. 3B is a fragmentary cross-sectional view of the assembled heatexchanger arrangement of FIG. 2 taken at section line 3B-3B.

DETAILED DESCRIPTION

In FIGS. 1A and 1B, a prior art cross flow heat exchanger (hereinafter“heat exchanger”) is shown comprising a first fin layer 100, a tubelayer 102, and a second fin layer 104.

The first fin layer 100 is formed as a corrugated sheet from a thinsheet of thermally conductive metal, such as copper, brass, aluminum orother light metal alloy. In the illustrated example, the corrugationsare in the form of a square wave in cross-section.

The first fin layer 100 is bonded to the tube layer 102 by soldering,brazing, welding, or other metal-to-metal attachment means that permitheat transfer from the tube layer 102 to the first fin layer 100.

By providing the first fin layer 100 as a repeating wave, a series ofenclosed channels 106 are formed for channeling a flow of air along thesurface of the tube layer 102. This intimate contact of the air in theenclosed channels 106 enhances the exchange of heat from the tube layer102 to the first fin layer 100.

The tube layer 102 is formed of individual elongate tubes 108 that arearranged in side-by-side relation. The elongate tubes 108 are formed ofa thermally conductive metal, typically copper, brass, aluminum or otherlight metal alloy. The elongate tubes 108 have flat walls disposedparallel to and bonded to the coplanar and flat bottom surfaces 110 ofthe first fin layer 100. A gap 112 is provided between each pair ofadjacent elongate tubes 108. This provides for some airflow between thecurved end walls 114 of the elongate tubes 108 and thus providesadditional heat transfer from the curved end walls 114 to the flow ofair passing through the enclosed channels 106.

The elongate tubes 108 extend in a direction perpendicular to thelongitudinal extent of the enclosed channels 106. In this manner, airflowing down the enclosed channels 106 can branch at each gap 112 andflow around the curved end walls 114 of the elongate tubes 108.

The second fin layer 104 is identical in construction and operation tothe first fin layer 100, but it is disposed on the opposite side of thetube layer 102 then the first fin layer 100.

This type of prior art heat exchanger is very effective when dealingwith clean, processed air. In vehicles that work in the field, such asdump trucks, front loaders, excavators, tractors, and particularlyagricultural harvesters, the large amount of contaminants in the air,and particularly longer and more elongate fibrous contaminants such aschaff, leaves, husks, and the like, can plug these heat exchangers. Theheat exchangers are plugged by contaminants traveling with the coolingairflow through the enclosed channels 106. When these contaminants reacha branch at each gap 112, they tend to fill the gaps 112 and plug them.

Worse, once the gaps 112 are plugged at any point, they tend to gatherother, smaller particles until the enclosed channels 106 are completelyfilled, thereby providing a complete blockage of air flow through theenclosed channel 106.

Even worse, once an enclosed channel 106 is blocked or partially blockedby contaminants, the increase in pressure in the blocked or partiallyblocked enclosed channel 106 will cause the airflow to bypass theblockage, spread out, pass through adjacent gaps 112 and be directedinto adjacent enclosed channels 106. This will laterally spreadcontaminants entering the blocked or partially blocked enclosed channel106 into adjacent enclosed channels 106, and adjacent gaps 112. Thisprocess causes a blockage in a single enclosed channel 106 to propagatelaterally and grow in size. This is due to the interconnected nature ofthe enclosed channels 106. The enclosed channels 106 are interconnectedby air flowing laterally (i.e. perpendicular to the longitudinal extentof the enclosed channels 106) down the length of the gaps 112 and intoadjacent enclosed channels 106.

Because these contaminants are wrapped around the curved end walls 114of the elongate tubes 108 they cannot be reached and cleaned by longrods or blasts of air that are forced down the enclosed channels 106.The contaminants remain trapped in these gaps 112 even after suchcleaning, and the efficiency of the heat exchanger is substantiallyreduced.

The new arrangement of FIG. 2 overcomes these problems with heat flowand cleaning by closing the gaps 112. In FIG. 2, the first fin layer100, the tube layer 102, and the second fin layer 104 are arranged withrespect to each other as provided in the prior art discussed above. Thefirst fin layer 100 and the tube layer 102 are separated by the additionof a fluid guide layer 200. The tube layer 102 and the second fin layer104 are separated by the addition of a fluid guide layer 202. Thefunction of the fluid guide layer 200 and the fluid guide layer 202 isto reduce or eliminate the airflow passing into the gaps 112. The fluidguide layer 200 and the fluid guide layer 202 prevent the airflow frombeing deflected into the gaps 112 and thereby preventing contaminants topass into the gaps 112. In this manner, contaminants cannot wrap aroundthe curved end walls 114 of each of the elongate tubes 108, accumulate,and eventually create a plug that cannot easily be removed.

The fluid guide layer 200 and the fluid guide layer 202 are in the formof thin, planar sheets. The fluid guide layer 200 and the fluid guidelayer 202 are formed of a thermally conductive metal, such as copper,brass, aluminum or other light metal alloy. As in the prior artarrangement of FIG. 1A and FIG. 1B, the elongate tubes 108 have flatwalls disposed parallel to and bonded to the coplanar and flat bottomsurfaces 110 of the first fin layer 100 and the second fin layer 104. Inthe embodiment of FIG. 2, however, the fluid guide layer 200 and thefluid guide layer 202 are bonded between the first fin layer 100 and thetube layer 102, and between the second fin layer 104 and the tube layer102, respectively.

The heat exchanger is formed in the manner suggested by FIG. 2. The tubelayer 102 is assembled by arranging the elongate tubes 108 in a regularorientation with the gap 112 between each tube. The first fin layer 100and the second fin layer 104 are formed from sheets into the corrugatedarrangement shown in FIG. 2. Once these layers are formed, the fluidguide layer 200 is disposed between the first fin layer 100 and the tubelayer 102, and the fluid guide layer 202 is disposed between the tubelayer 102 and the second fin layer 104. The layers are then broughttogether and are mechanically bonded, preferably by soldering, brazing,or welding the now-abutting layers together.

When this assembly process is complete the heat exchanger has theappearance shown in FIG. 3A and FIG. 3B. As best shown in FIG. 3A, thefluid guide layer 200 encloses the open bottom of each enclosed channel106, extending substantially the entire length of each enclosed channel106 and preventing air from passing out of the enclosed channel 106 andinto the gaps 112 between the elongate tubes 108. As best shown in FIG.3B, the fluid guide layer 200 and the fluid guide layer 202 encloseopposing sides of the gap 112, extending substantially the entire lengthof each elongate tube 108. In this manner, air with entrainedcontaminants is prevented from entering the gaps 112 and travelinglaterally through the gaps 112 and into adjacent enclosed channels 106.

A further advantage to this arrangement is that the fluid guide layer200 and the fluid guide layer 202 form a continuous smooth bottom toeach of their respective enclosed channels 106. This reducesirregularities in the cross-section of each enclosed channel 106 andthus reduces the possibility of contaminants becoming entrapped in anyof the enclosed channels 106.

What has been illustrated and described herein is a cross flow heatexchanger, with a first fluid (e.g. liquid) flow in the elongate tubes108 traveling transverse to a second fluid (e.g. gas or air) flow in theenclosed channels 106. Typically, manifolds are coupled to the open endsof the enclosed channels 106 and the elongate tubes 108 to distribute(at their inlet ends) and to gather (at their outlet ends) the fluidflow. Such manifolds are of conventional arrangement and have not beenillustrated herein for convenience since they do not form a part of theinvention.

The arrangements illustrated and described herein are merely examples ofone way to create the invention. Someone skilled in the art of thisinvention would readily see other ways to create the invention thatwould fall within the scope of the claims. It is the claims that definethe scope of the invention.

For example, the corrugated pattern, shown here as a square wave mayhave a different cross sectional pattern, such as a sine wave, saw toothwave, trapezoidal wave, or other repeating pattern. The particularpattern will depend upon the particular cooling requirements, sheetthickness, and cross-sectional area of the enclosed channels 106.

As another example, the elongate tubes 108 shown herein have opposingflat sides and rounded ends (the “ends” in this context meaning theportion of the elongate tubes 108 that face into and define the gap112). The elongate tubes 108 could have a variety of othercross-sectional shapes, such as a circle, a square, rectangle, or anoval, as just a few examples.

As another example, if the fluid guide layer 200 encloses one side ofthe gaps 112 over their entire length and the second fluid guide layer202 encloses the other side of the gaps 112 over their entire length,the gaps 112 themselves can form an additional fluid flow channel forthe fluid passing through the elongate tubes 108 by keeping the fluidpassing through the gaps 112 separate from the fluid passing through theenclosed channels 106.

As another example, the arrangements illustrated herein shows two fluidguide layers 200, 202 separating two fin layers 100, 104 from both sidesof the tube layer 102. For reasons of space and economy of construction,only a single fluid guide layer 200 and a single fin layer need to beused.

As another example, the arrangements discussed herein refer to the fluidpassing through the first fin layer 100 and the second fin layer 104 asair (a gas). Alternatively, the fluid passing to the first fin layer 100and the second fin layer 104 may be a liquid.

I claim:
 1. A heat exchanger for a work vehicle, comprising: a tubelayer (102) comprised of a plurality of elongate tubes (108), whereinthe plurality of elongate tubes (108) are spaced apart by gaps (112) andare oriented parallel to each other in a first direction, wherein eachof the plurality of elongate tubes (108) defines a channel for passing afirst fluid therethrough; a first fin layer (100) in a form of acorrugated sheet having a plurality of corrugations, in which theplurality of corrugations of the first fin layer (100) extend in asecond direction transverse to the first direction, and wherein thefirst fin layer (100) is disposed parallel to the tube layer (102) andon a first side of the tube layer (102), and wherein each of theplurality of corrugations of the first fin layer (100) facing the tubelayer (102) define an enclosed channel (106) for passing therethrough afluid different from the first fluid; and a first fluid guide layer(200) formed of a continuous, generally planar sheet that extends acrossand encloses the plurality of corrugations of the first fin layer (100)over substantially an entire length of the plurality of corrugations. 2.The heat exchanger of claim 1, further comprising a second fin layer(104) in a form of a corrugated sheet having a plurality ofcorrugations, in which the plurality of corrugations of the second finlayer (104) extend in the second direction, and wherein the second finlayer (104) is disposed parallel to the tube layer (102) and on a secondside of the tube layer (102) that is opposite to the first side of thetube layer (102), and wherein the plurality of corrugations of thesecond fin layer (104) facing the tube layer (102) define channels (106)for passing therethrough a fluid different from the first fluid; and asecond fluid guide layer (202) formed of a continuous, generally planarsheet that extends across and encloses the plurality of corrugations ofthe second fin layer (104) over substantially an entire length of theplurality of corrugations.
 3. The heat exchanger of claim 1, wherein thefirst fluid guide layer (200) extends across and encloses the gaps (112)over substantially an entire length of the gaps (112).
 4. The heatexchanger claim 1, wherein the first fin layer (100) comprises metal andthe first fluid guide layer (200) comprises metal, and wherein the firstfin layer (100) is bonded to a first side of the first fluid guide layer(200) by a process selected from a group comprising soldering, brazing,and welding.
 5. The heat exchanger of claim 4, wherein the tube layer(102) comprises metal and wherein the tube layer (102) is bonded to asecond side of the first fluid guide layer (200) by a process selectedfrom a group comprising soldering, brazing, and welding.
 6. The heatexchanger of claim 1, wherein none of the channels (106) has an interiorregion that is in fluid communication with an interior region of any ofthe plurality of elongate tubes (108).
 7. The heat exchanger of claim 1,wherein the channels (106) are rectangular in cross section.
 8. The heatexchanger of claim 7, wherein the channels (106) are square incross-section.